We propose a three year study to continue investigation of facial behavior related to various types of dental pain: Phasic pain -- brief acute pain such as pain in response to dental injection, or, as a laboratory model, pain in response to electrical tooth pulp stimulation; Tonic pain -- longer term acute pain such as pathologic pain of tooth pulp infection, or as a laboratory analogue, cold pressor pain; and Chronic pain -- persistent orofacial pain such as TMJ/MPD. Four issues are addressed: I - The further description and validation of facial behavior measures of these three types of pain; II - Evaluation of the role of facial expression in the communication of pain in dental care settings; III - Evaluation of the manipulation of facial behavior as a potential clinical pain control strategy; IV - Exploration of the relationships among brain activity, facial expression and various types of pain. Videotape records of facial behavior will be collected in the laboratory and clinical treatment settings while research pain measurement is conducted. The video records will be systematically sampled and samples coded using the highly reliable Facial Action Coding System to derive measures of frequency, intensity and duration of facial expressions of pain and negative affect. These measures will be compared with subjective pain report, as measured by visual analogue scales and category scales for reporting sensory, cognitive and affective dimensions of pain, in order to validate facial expression measures for the various types of pain. Brain activity will be recorded to derive cortical power spectrum analyses of the EEG and pain related brain evoked potentials. Analysis of relationships among measures of facial expression accompanying pain, verbal reports of pain and physiologic indices of brain activity will be conducted; and we will observe how these relationships change when the patients are instructed to suppress or mask a facial expression of pain. The sensitivity of dentists to facial expressions of pain will also be assessed using videotape segments of facial expression accompanying clinical pain. We currently rely almost exclusively on subjective verbal behavior for reporting the sensory, cognitive and affective dimensions of pain. Quantification of the nonverbal facial behavior accompanying pain should enhance our ability to evaluate the significance of human pain complaint.